How to discover Windows computers using SNMP via SCOM

If you want to discover Windows computers using SNMP, it fails.
Windows computers running SNMP are filtered out of discovery results if:

• The device type is “Host” and the vendor is “Microsoft”
• The sysDescription field contains “Microsoft”
• The sysOid starts with .1.3.6.1.4.1.311.1.1.3.1
• The sysOid contains 1.3.6.1.4.1.199.1.1.3.11

(ref: http://technet.microsoft.com/en-us/library/hh212935.aspx).

Edit the ic-post-processor.asl file in the “C:\Program Files\System Center 2012\Operations Manager\Server\NetworkMonitoring\rules\discovery” directory for solve this problem.

ISWINDOWSHOST(systemObj) do {
    IF (systemObj->TYPE == "HOST" && systemObj->Vendor == "MICROSOFT") {
        RETURN TRUE ;  /* change to FALSE */
    }
 
    IF (SEARCHSTRING(systemObj->Description, "Windows")) {
        RETURN TRUE ;  /* change to FALSE */
    }
 
    systemOIDCheck = ".1.3.6.1.4.1.311.1.1.3.1" ;
    IF (SUBSTRING(systemObj->SystemObjectID, 0, sizeof(systemOIDCheck)) == systemOIDCheck) {
        RETURN TRUE ;  /* change to FALSE */
    }
 
    systemOIDCheck = ".1.3.6.1.4.1.99.1.1.3.11" ;
    IF (SUBSTRING(systemObj->SystemObjectID, 0, sizeof(systemOIDCheck)) == systemOIDCheck) {
        RETURN TRUE ;  /* change to FALSE */
    }
    RETURN FALSE ;
}